Banded knifefish - Gymnotus carapo

Body shape and the overall appearance are strongly reminiscent of a knifefish, but it's not one I'm familiar with.

Looks like a Gymnotus knifefish of some sort.

Thanks @Great Argus and @Zooish ! Did myself some research ( with the info you both provided ) and found that the Banded knifefish - Gymnotus carapo was kept at this Aquarium in 2016 and Zootierliste mention it as being a species formerly kept at this Aquarium but that it was not seen and signed in 2017.
As it however seems, the species is still kept .